This invention relates to a system for securing and restraining a patient undergoing examination by means of a medical diagnostic imaging device. More specifically, this invention relates to such a system for use with computerized tomography (CT) and nuclear magnetic resonance (NMR) imaging apparatus, for example.
In many medical diagnostic imaging procedures, it is frequently either necessary or desirable to secure and restrain a patient to the patient-supporting cradle. For example, it may be necessary to secure and restrain the patient to avoid accidental falls off the cradle. As will be more fully described hereinafter, it may also be necessary to secure and restrain the patient to minimize body motion during the imaging procedure. In the case of uncooperative patients, the security and restraint system additionally provides the means to control an otherwise combative patient.
One of the imaging procedures which requires the patient to remain motionless for a substantial length of time during the data-collecting process is NMR imaging. In NMR imaging, the data is collected by subjecting the patient to various magnetic fields and radio-frequency pulses. During the data acquisition period (which may extend for several minutes or longer), the patient must remain substantially motionless so that sufficient data is collected to reconstruct images which are free of motion-related artifacts. Another reason for the prolonged data collecting period is so that the signal-to-noise ratio of the collected data is within the required limits for obtaining good image quality. In computerized tomography, the problem of patient motion is less severe since, as is known, scan time is typically of the order of seconds. Nonetheless, for the reasons given hereinabove, it is desirable that the patient remain motionless during the scanning operation. In the computed projection radiography method, which employs the same apparatus as computerized tomography, the patient is advanced longitudinally through a fan-shaped X-ray beam at a constant velocity for undergoing a line-by-line scan. It will be appreciated, therefore, that during this procedure it is again desirable that the patient remain motionless so as to ensure high image quality.
It is important to note that the patient security and restraint system must be configured to comfortably accommodate patients of various sizes. The restraints must also be movable along the cradle so as to secure various parts of the body, such as arms, chest, knees, and ankles, as necessary. In order to esure prompt care of the patient in the event of an emergency, the restraints must be removable quickly and easily. For use in apparatus, such as computerized tomography utilizing ionizing radiation, the restraints must be substantially transmissive to the X-ray radiation. In NMR imaging, the materials must be non-ferromagnetic to avoid distrubing the homogeneity of the carefully controlled magnetic field needed for obtaining imaging information. It is, therefore, a principal object of the invention to provide a patient security and restraint system which satisfies the constraints described.